- Joined
- Jun 4, 2023
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- 15
I have a restored PL4000 that after a few weeks of running perfectly with no issues at all, now will not (or appears) not to shut down completely.
Yesterday, I turned it on and the connected 400 amp and 5000 receiver came on as expected but there was a louder than normal hum coming from the setup. Usually I can hear the hum of the 400 transformer a bit, but it's not too bad. This time the hum was significantly louder, so I shut the system down. The 400 and 5000 shut down as expected and the PL4000 internal relay disengaged, or at least it makes the disengagement sound like normal. But the PL4000 pilot light remained on until I unplugged the PL4000. Looking at the schematic I can see that the LED is clearly in the power circuit but I'm left wondering why the LED is on and IS the unit actually on, or just appears to be on due to the LED being ON. Possibly a component failure that leaves a sufficient voltage to the LED but the unit and signal path and non-operational? The AC outlets on the preamp appear to be working normally.
I suspect perhaps this behavior has been seen before by someone out here and thought I'd ask. If you have seen this behavior, or have a recommendation for further trouble shooting I would appreciate any assistance.

Yesterday, I turned it on and the connected 400 amp and 5000 receiver came on as expected but there was a louder than normal hum coming from the setup. Usually I can hear the hum of the 400 transformer a bit, but it's not too bad. This time the hum was significantly louder, so I shut the system down. The 400 and 5000 shut down as expected and the PL4000 internal relay disengaged, or at least it makes the disengagement sound like normal. But the PL4000 pilot light remained on until I unplugged the PL4000. Looking at the schematic I can see that the LED is clearly in the power circuit but I'm left wondering why the LED is on and IS the unit actually on, or just appears to be on due to the LED being ON. Possibly a component failure that leaves a sufficient voltage to the LED but the unit and signal path and non-operational? The AC outlets on the preamp appear to be working normally.
I suspect perhaps this behavior has been seen before by someone out here and thought I'd ask. If you have seen this behavior, or have a recommendation for further trouble shooting I would appreciate any assistance.

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